共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Schulin-Zeuthen E. Kebreab J. Dijkstra S. Lopez A. Bannink H. Darmani Kuhi J.H.M. Thornley J. France 《Animal Feed Science and Technology》2008,143(1-4):314
This study was undertaken to introduce the Schumacher equation and compare it with established functions for describing growth in pigs. The relationship between live weight (LW) and cumulative feed intake was also investigated. A database was constructed from three independent trials in which LW, age and intake were measured from birth to 937 days. Three growth functions were used for analysis of growth versus age: Gompertz, Schumacher and Weibull; and the Richards and monomolecular equations were used for analysis of cumulative feed intake versus LW. The growth functions have different points of inflexion. Liveweight at inflexion is Wf/e for the Gompertz, where Wf is the final weight, Wf/e2 for the Schumacher, and Wf − (Wf − W0) exp[−(n − 1)/n] for the Weibull, where W0 is initial body weight and n is a shape parameter. Meta-analysis of the data using mixed model and nonlinear regression procedures was conducted to identify the most appropriate growth function. Functions were compared using F-tests or Bayesian Information Criteria, which give a value based on best fit and number of parameters in the model. The three equations were fitted to five individual pig growth profiles and to the composite data. Although the Weibull had a lower residual mean square, it did not significantly improve the fit compared to the simpler models and appears to be over-parameterised. The results suggest that model selection should be based on the type and amount of data available for analysis. Residuals plot showed that Schumacher and Weibull better predict the initial growth phase, however, all models showed largest magnitude of residuals towards the end of the growth profile. The monomolecular equation was most appropriate for describing LW against cumulative feed intake and may be used to formulate diets based on the efficiency of conversion of feed to LW at various stages of the animal's life span. 相似文献
2.
A response surface methodology (RSM) was developed for predicting the growth rate of Bacillus cereus in a tryptic soy broth medium as a function of temperature (10 to 40°C), pH (5.5 to 8.5), and the NaCl concentration (0 to
8%). The primary model showed a good fit (r2 = 0.920 to 0.999) to a Gompertz equation to obtain growth rates each condition. The quadratic polynomial model was found
to be significant (p < 0.0001) and predicted values were found to be in good agreement with experimental values (R2 value of 0.9486). The evaluation of RSM for describing the growth rate of B. cereus used the bias factor (Bf) and the accuracy factor (Af). Both the Bf value (1.11) and the Af value (1.50) were within acceptable ranges. This model was provided an efficient and accurate method for predicting the growth
of B. cereus as a function of the controlling factors. 相似文献
3.
This study was attempted to develop a new exponential sum model to describe the effect of temperature on growth rate (GR)
of Escherichia coli O157:H7 in broth. The growth rates of E. coli O157:H7 at different storage temperatures (4, 10, 15, 20, 25, 30, and 35°C) estimated by fitting with the modified Gompertz
model were used to develop secondary models such as square root model, Ratkowsky model and exponential sum model. Measures
of coefficient of determination (R
2), root mean square error (RMSE) and the sum of squares due to error (SSE) were employed to compare the performances of these
three secondary models. Based on these criteria, the developed exponential sum model showed the better goodness-of-fit and
performance. 相似文献
4.
5.
Y. Tsukahara Y. Chomei K. Oishi A.K. Kahi J.M. Panandam T.K. Mukherjee H. Hirooka 《Small Ruminant Research》2008,80(1-3):8-15
The objective of this study was to investigate growth patterns of goats utilizing data from a crossbreeding program involving the exotic German Fawn (GF) and the indigenous Kambing Katjang (KK) goats. Growth curve models and growth curve parameters were compared and analyzed for different genotypes and litter types. A total of 20,393 weight–age data from 208 female goats belonging to various crossbreeding genotypes were individually fitted to four growth curve models (Brody, Bertalanffy, Gompertz and Logistic). The goodness of fit was highest in the Brody model in most cases. A comparison of R2 among genotypes showed that they were highest for KK. There were no significant differences of genotypes for estimated mature weight in the Brody model. The estimated mature weights for KK were significantly lower (P < 0.05) than for GF × KK (F1), backcrosses with 75% GF genes (BC) and F1 × F1 (F2) in the other models. The correlations between estimated mature weights and the maturing rates were lowest for BC. The genotype significantly (P < 0.01) affected the age at the constant degree of maturity (67% and 90% of mature weight) in all models. The BC genotype was the youngest at maturity and KK the oldest. All models well expressed the growth pattern of the target animals when they were older than 2.5 years of age. The results from the present study showed that the growth pattern may be altered by crossbreeding of KK with the GF breed. 相似文献
6.
M. De Giusti C. Aurigemma L. Marinelli D. Tufi D. De Medici S. Di Pasquale C. De Vito A. Boccia 《Journal of applied microbiology》2010,109(3):996-1006
Aims: The study was performed to evaluate the safety of whole and RTE vegetables and to investigate the effectiveness of different preventive strategies for the quality assurance of RTE vegetables collected from three Italian production systems. Producer 1, applied a strict system in compliance with GAP‐ GMP – HACCP, Producer 2 used chlorine disinfection at a second washing step, and Producer 3 using a physical microbial stabilization. Methods: During the period 2005–2007, a total of 964 samples including whole vegetables and RTE salads, collected from three different producers in central Italy, were analysed to quantify the aerobic mesophilic count (AMC) and Escherichia coli, and for the presence of Salmonella spp, Listeria monocytogenes, E. coli O157:H7, hepatitis A virus and Norovirus (NoV). Results: None of the whole vegetable samples were positive for L. monocytogenes, E. coli O157:H7, HAV and NoV; however, a low prevalence of Salmonella was found. No pathogens were detected with cultural methods in any of the RTE vegetables analysed, only two RTE samples were positive for L. monocytogenes with PCR, but were not confirmed by the cultural method. The median values of AMC in RTE vegetables measured 24 h after packaging were statistically different among the 3 producers (5·4 × 106, 1·5 × 107 and 3·7 × 107 CFU g?1, respectively; P = 0·011). The lowest level was detected in Producer 1. Conclusion: The products that were processed applying rigorously GAP, GMP and HACCP showed a better microbiological quality than those processed with chemical or physical stabilization. Study Significance and Impact: The results of the study evidenced the efficacy of GAP, GMP and HACCP in improving microbiological quality of whole and RTE vegetables. 相似文献
7.
Marcelo Javier Kittlein 《Population Ecology》2009,51(1):143-151
The ability of four mechanistic population models to mirror a 5-year time series of seasonal densities of the pampas mouse,
Akodon azarae, from central Argentina, is evaluated in this paper. The different models included, singly or in combination, the effects
of a putative competitor and a specialist predator on the dynamics of pampas mice. The most simple model, a logistic single-species
stochastic differential equation, failed to fit the observed time series satisfactorily (R
model2 = 0.36), while models including interspecific effects gave much better fits with increasing model complexity (competition
R
model2 = 0.71, predation R
model2 = 0.62, competition and predation R
model2 = 0.83). Using Akaike’s information criterion, the competition model was selected as the best alternative with regard to
model fit and model complexity. Synthetic time-series probes obtained by simulations from the parameterized stochastic mechanistic
models were significantly different and indicated the competition plus predation model as a slightly better alternative than
the competition model. The differences between the two methods for selecting models indicate that the incorporation of predation
only slightly improves the match between the predicted and observed time series and that this slight improvement is not sufficient
to override the increase in model complexity. Competition thus seems to play a more important role than predation in shaping
the population dynamics of pampas mice. 相似文献
8.
Laurel J. Haavik James R. Meeker Wood Johnson Kathleen Ryan Jean J. Turgeon Jeremy D. Allison 《Entomologia Experimentalis et Applicata》2013,149(2):177-184
The study of temporal interactions between native insects and alien invaders can be facilitated by the ability to forecast adult emergence. We used field‐collected adult emergence data of Sirex noctilio Fabricius (Hymenoptera: Siricidae), a woodwasp native of Eurasia that has recently invaded northeastern North America, and Sirex nigricornis Fabricius, a woodwasp native to North America, to develop and test cumulative degree‐day (CDD) models. Five data sets were collected each in Ontario, Canada (S. noctilio) and Louisiana, USA (S. nigricornis) over 4 years; three data sets were used to develop models and two were used to test them. Males and females of each species were modelled separately. After testing several potential temperatures, chosen thresholds for CDD were 0 °C lower threshold and 25 °C upper threshold for both Sirex spp. We used a three‐parameter Gompertz growth function to model Sirex spp. emergence against CDD. Models predicted 10% emergence of S. noctilio in Ontario after 1 239 and 1 280 CDD, for males (start date = 1 April; R2 = 0.91) and females (start date = 1 April; R2 = 0.86), respectively. Models predicted 10% emergence of S. nigricornis in Louisiana after 3 980 and 5 016 CDD, for males (start date = 1 May; R2 = 0.83) and females (start date = 1 March; R2 = 0.73), respectively. Cumulative degree‐day models predicted 10 and 90% emergence of woodwasp populations with less error (1–13%) than they did 50% emergence (5–27%). For both Sirex spp., male emergence began a few days before and concluded at about the same time as that of females. In southern Ontario, models predict that S. noctilio adults will be in flight between 1 015 and 2 430 CDD (1 April start date for CDD; from early‐July until mid‐September). In Louisiana, models predict that S. nigricornis adults will be in flight between 3 854 and 4 700 CDD (1 May start date for CDD; from early‐October until late‐November). 相似文献
9.
Ma.?del?Carmen?Chávez-Parga Omar?González-Ortega Guadalupe?Sánchez-Cornejo Ma.?de?la?Luz?X.?Negrete-Rodríguez Guillermo?González-Alatorre Eleazar?M.?Escamilla-Silva
Summary Growth of Gibberella fujikuroi in submerged cultures occurs as micelles or filamentous hyphae dispersed in fluid and pellets or stable, spherical agglomerations. Gibberella fujikuroi growth, substrate consumption and bikaverin production kinetics obtained from submerged batch fermentation were fitted to three different sigmoid models: two and three-parameter Gompertz models and one Logistic model. Growth fitting was used to compare between models and select the best one by means of an F test. The best model for describing growth was the two-parameter Gompertz model and was used for glucose consumption and bikaverin production fitting. Data from eight different schemes of fermentations were analysed and parameter estimation was carried out by means of minimization of residual sum of squares. Some characteristic values obtained with the two-parameter Gompertz model fit are: μ=0.028 h−1, Yx/s=0.1089 g substrate/g biomass, α =0.1384 g product/g biomass. 相似文献
10.
M.S. Schvartzman X. Belessi F. Butler P. Skandamis K. Jordan 《Journal of applied microbiology》2010,109(5):1790-1799
Aim: To determine growth initiation differences of Listeria monocytogenes between a cheesemaking context, milk and tryptic soy broth (TSB). Methods and Results: A laboratory‐scale cheese was made with a mix of two strains of L. monocytogenes at four initial pH values, five water activity (aw) values and two contamination levels at 30°C. Counts of L. monocytogenes were determined at time 0 and after 8 h of cheese manufacture. Milk and TSB at the same pH and aw conditions were inoculated with the L. monocytogenes mix in multi‐well plates. Growth was determined by plating each well onto Agosti & Ottaviani Listeria Agar after 8 h of incubation at 30°C. Each condition was repeated six times, and growth initiation probability was modelled with logistic regression models. Growth initiation boundaries were obtained for each matrix type. The results showed that the growth limits were matrix dependent. In the three matrix types, aw was the most important factor affecting the probability of growth initiation. Contamination level affected growth TSB and cheesemaking conditions. Conclusions: The interface wideness and position in cheese, milk and TSB were dissimilar, indicating that the use of models evaluated in TSB or milk could not be used to predict the behaviour of L. monocytogenes under cheesemaking conditions. Significance and Impact of the Study: Predictive models generated in liquid media are not necessarily adaptable to solid food, and the generation of real food models is necessary. 相似文献
11.
L. Garcia‐Gonzalez A. Rajkovic A.H. Geeraerd K. Elst L. Van Ginneken J.F. Van Impe F. Devlieghere 《Letters in applied microbiology》2010,50(6):653-656
Aims: The objective of this study was to investigate whether bacterial cells could develop resistance (as a part of their adaptation strategy) to high‐pressure CO2 (HPCD) inactivation. Methods and Results: Alternating cycles of exposure to pressurized CO2 (10·5 MPa, 35°C, 400 min?1, 70% working volume ratio during 10 min) and re‐growth of the surviving subpopulation were used to investigate possible increases in the resistance of Escherichia coli and Listeria monocytogenes to HPCD. The results show an increased resistance of both pathogens tested after seven cycles of inactivation. Increase in the resistance after 15 cycles resulted in a difference of 2·4 log CFU ml?1 in log N0/Ni when parental (N0) and treated cultures (Ni) of E. coli and L. monocytogenes were compared. Conclusions: Current findings indicate the ability of micro‐organisms to adapt to HPCD preservation technology. Significance and Impact of the Study: The occurrence of HPCD‐resistant micro‐organisms could pose a new hazard to the safety and stability of HPCD‐processed foods. 相似文献
12.
Lettuce (Lactuca sativa) transformation varies by genotype. Various culture parameters have been studied in order to improve the transformation efficiency
of lettuce cultivars. However, no improved transformation procedure for recalcitrant lettuce cultivars has yet been established.
Here, we demonstrate the effects of varying concentrations and distinct combinations of growth regulators on recalcitrant
lettuce transformation efficiency. More precisely, we assessed differences in the effects of several growth regulator combinations,
including N-6(2-isopentenyl)-adenine (2ip), on induction of callus and regeneration of shoots after co-cultivation with Agrobacterium. When two commercial recalcitrant cultivars, Red Romaine and Bibb, were cultured on a medium with 2ip 1 mg l−1, IAA 0.1 mg l−1, and subsequently transferred to a second medium with BA 0.4 mg l−1, NAA 0.05 mg l−1 for selection and shoot regeneration, transformation efficiencies reached 8 and 9%, respectively. Stable integration and
transmission of the transgene in T1 generation plants were confirmed by molecular analysis. This procedure represents a simple,
efficient, and general means of transforming various lettuce cultivars, including recalcitrant commercial cultivars. 相似文献
13.
Sexual size dimorphism (SSD) is widespread in animals, especially in lizards (Reptilia: Squamata), and is driven by fecundity selection, male–male competition, or other adaptive hypotheses. However, these selective pressures may vary through different life history periods; thus, it is essential to assess the relationship between growth and SSD. In this study, we tracked SSD dynamics between a “fading‐tail color skink” (blue tail skink whose tail is only blue during its juvenile stage: Plestiodon elegans) and a “nonfade color” tail skink (retains a blue tail throughout life: Plestiodon quadrilineatus) under a controlled experimental environment. We fitted growth curves of morphological traits (body mass, SVL, and TL) using three growth models (Logistic, Gompertz, and von Bertalanffy). We found that both skinks have male‐biased SSD as adults. Body mass has a higher goodness of fit (as represented by very high R2 values) using the von Bertalanffy model than the other two models. In contrast, SVL and TL for both skinks had higher goodness of fit when using the Gompertz model. Two lizards displayed divergent life history tactics: P. elegans grows faster, matures earlier (at 65 weeks), and presents an allometric growth rate, whereas P. quadrilineatus grows slower, matures later (at 106 weeks), and presents an isometric growth rate. Our findings imply that species‐ and sex‐specific trade‐offs in the allocation of energy to growth and reproduction may cause the growth patterns to diverge, ultimately resulting in the dissimilar patterns of SSD. 相似文献
14.
Santiago A. Barbini David E. Sabadin Jorge M. Román Pablo A. Scarabotti Luis O. Lucifora 《Journal of fish biology》2021,99(4):1328-1340
The spotback skate Atlantoraja castelnaui (Arhynchobatidae) is a large and threatened skate species subjected to fishing pressure, endemic to the Southwest Atlantic that occurs from Rio de Janeiro, Brazil, to San Jorge Gulf, Argentina. The age, growth, age at maturity and the maximum intrinsic rate of population increase rmax of A. castelnaui were studied using 152 specimens collected from off Uruguay and north Argentina (35°–42° S), between June 2013 and February 2020. Vertebrae from 143 individuals were used for ageing (females: n = 83, size range 404–1300 mm total length, TL; males: n = 60, size range 400–1270 mm TL). Maximum ages determined for females and males were 30 and 28 years, respectively. To fit growth models, non-linear and Bayesian estimation approaches were considered. For the first approach, a set of four candidate growth (size-at-age) models were fitted: three-parameter von Bertalanffy, two-parameter von Bertalanffy with fixed L0, Gompertz and Logistic. In the second approach, von Bertalanffy, Gompertz and Logistic were fitted. For non-linear estimation, model selection indicated that the entire set of candidate growth models were supported by the data. The von Bertalanffy was selected as the best model for Bayesian estimation. There were no differences in growth between sexes. For the sexes combined, the von Bertalanffy growth model by Bayesian method was considered the most adequate to describe the growth of A. castelnaui (growth mean parameters ± S.D. : L∞ = 1210.29 ± 40.68 mm; k = 0.12 ± 0.01 years−1; L0 = 179.20 ± 11.62 mm). The age at maturity was estimated at 16.21 and 14.04 years for females and males, respectively. The maximum intrinsic rate of population increase rmax was estimated as 0.252 years−1. Life-history traits and rmax provided in the present study suggest that this species has a relatively low productivity and may be vulnerable to an intense fishing pressure. 相似文献
15.
Leaf area estimation is an important biometrical observation recorded for evaluating plant growth in field and pot experiments.
In this study, conducted in 2009, a leaf area estimation model was developed for aromatic crop clary sage (Salvia sclarea L.), using linear measurements of leaf length (L) and maximum width (W). Leaves from four genotypes of clary sage, collected
at different stages, were used to develop the model. The actual leaf area (LA) and leaf dimensions were measured with a Laser
Area meter. Different combinations of prediction equations were obtained from L, W, product of LW and dry mass of leaves (DM)
to create linear (y = a + bx), quadratic (y = a + bx + cx2), exponential (y = aebx), logarithmic (y = a + bLnx), and power models (y = axb) for each genotype. Data for all four genotypes were pooled and compared with earlier models by graphical procedures and
statistical measures viz. Mean Square Error (MSE) and Prediction Sum of Squares (PRESS). A linear model having LW as the independent variables (y
= −3.4444 + 0.729 LW) provided the most accurate estimate (R
2 = 0.99, MSE = 50.05, PRESS = 12.51) of clary sage leaf area. Validation of the regression model using the data from another
experiment showed that the correlation between measured and predicted values was very high (R
2
= 0.98) with low MSE (107.74) and PRESS (26.96). 相似文献
16.
Hayes RJ McHale LK Vallad GE Truco MJ Michelmore RW Klosterman SJ Maruthachalam K Subbarao KV 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(4):509-517
Verticillium wilt of lettuce caused by Verticillium dahliae can cause severe economic damage to lettuce producers. Complete resistance to race 1 isolates is available in Lactuca sativa cultivar (cv.) La Brillante and understanding the genetic basis of this resistance will aid development of new resistant
cultivars. F1 and F2 families from crosses between La Brillante and three iceberg cultivars as well as a recombinant inbred line population derived
from L. sativa cv. Salinas 88 × La Brillante were evaluated for disease incidence and disease severity in replicated greenhouse and field
experiments. One hundred and six molecular markers were used to generate a genetic map from Salinas 88 × La Brillante and
for detection of quantitative trait loci. Segregation was consistent with a single dominant gene of major effect which we
are naming Verticillium resistance 1 (Vr1). The gene described large portions of the phenotypic variance (R
2 = 0.49–0.68) and was mapped to linkage group 9 coincident with an expressed sequence tag marker (QGD8I16.yg.ab1) that has
sequence similarity with the Ve gene that confers resistance to V. dahliae race 1 in tomato. The simple inheritance of resistance indicates that breeding procedures designed for single genes will
be applicable for developing resistant cultivars. QGD8I16.yg.ab1 is a good candidate for functional analysis and development
of markers suitable for marker-assisted selection. 相似文献
17.
Prediction of membrane fouling in MBR systems using empirically estimated specific cake resistance 总被引:1,自引:0,他引:1
The focus of this study was to empirically estimate the specific cake resistance (SCR) by the variation in shear intensity (G) in four laboratory-scale MBRs. The control reactor (MBR0) was operated with aeration only while other MBRs (MBR150, MBR300 and MBR450) were operated with aeration and mechanical mixing intensities of 150, 300 and 450 rpm, respectively. It was found that the SCR was strongly correlated (R2 = 0.99) with the fouling rates in the MBRs. Moreover, the contribution of cake resistance (Rc) to the total hydraulic resistance (Rt) was predominant compared to the irreversible fouling resistance (Rf). On this basis, the cake filtration model was selected as a predictive tool for membrane fouling. This model was modified by replacing the SCR with its empirical shear intensity relationship. The modified model can predict the fouling rate for a given shear intensity (G) within 80 and 250 s−1 in a MBR system. 相似文献
18.
To gain insight into the metabolic design of the amino acid carrier systems in fish, we injected a bolus of 15N amino acids into the dorsal aorta in mature rainbow trout (Oncorhynchus mykiss). The plasma kinetic parameters including concentration, pool size, rate of disappearance (R
d), half-life and turnover rate were determined for 15 amino acids. When corrected for metabolic rate, the R
d values obtained for trout for most amino acids were largely comparable to human values, with the exception of glutamine (which
was lower) and threonine (which was higher). R
d values ranged from 0.9 μmol 100 g−1 h−1 (lysine) to 22.1 μmol 100 g−1 h−1 (threonine) with most values falling between 2 and 6 μmol 100 g−1 h−1. There was a significant correlation between R
d and the molar proportion of amino acids in rainbow trout whole body protein hydrolysate. Other kinetic parameters did not
correlate significantly with whole body amino acid composition. This indicates that an important design feature of the plasma-free
amino acids system involves proportional delivery of amino acids to tissues for protein synthesis. 相似文献
19.
Despite species in the Rubus fruticosus complex (wild blackberry) being among the most invasive plants globally in regions with large annual fluctuations in water
availability, little is known about their water relations. We compared water relations of a prominent member of the complex,
R. armeniacus (Himalayan blackberry), with species native to the Pacific Northwest of North America (PNW), R. spectabilis (salmonberry) and R. parviflorus (thimbleberry). In eight stands of each species located near Portland, Oregon, USA, we measured mid-day hydraulic resistance
(R
plant), and daily time series of stomatal conductance (g
s), leaf water potential (Ψlf), and environmental conditions at four time periods spanning the 2007 growing season. Although all species maintained Ψlf above −0.5 MPa in spring, R. armeniacus maintained less negative Ψlf (≥−1.0 MPa) than the natives in summer, a factor attributable to advantages in both its root and shoot systems. R
plant of R. armeniacus was ≤0.1 MPa mmol−1 m2 s for the duration of the study, and approximately 25–50% of R
plant for the native species in summer. R. armeniacus had higher g
s compared to the native species throughout the spring and summer, with approximately twice their rates in summer. Our R
plant and g
s results show that R. armeniacus has access to more water during PNW summers than congeneric natives, allowing it to maintain high water-use, and potentially
helping it achieve higher growth and reproductive rates. Water relations may therefore be a critical component of the competitive
and invasive success of R. armeniacus and other R. fruticosus species worldwide. 相似文献
20.
Zeinab Salehi Farzaneh Vahabzadeh Morteza Sohrabi Shohreh Fatemi Hussein Tawfiq Znad 《Biodegradation》2010,21(4):645-657
The effect of p-nitrophenol (PNP) concentration with or without glucose and yeast extract on the growth and biodegradative capacity of Ralstonia eutropha was examined. The chemical constituents of the culture medium were modeled using a response surface methodology. The experiments
were performed according to the central composite design arrangement considering PNP, glucose and yeast extract as the selected
variables whose influences on the degradation was evaluated (shaking in reciprocal mode, temperature of 30°C, pH 7 and test
time of about 9 h). Quadratic polynomial regression equations were used to quantitatively explain variations between and within
the models (responses: the biodegradation capacity and the biomass formation). The coefficient of determination was high (R
adjusted2 = 0.9783), indicating the constructed polynomial model for PNP biodegradative capacity explains the variation between the
regressors fairly well. A PNP removal efficiency of 74.5% occurred within 9 h (15 mg/L as the initial concentration of PNP
with use of yeast extract at 0.5 g/L). 相似文献